Impact of calcium on the interactions between epigallocatechin-3-gallate and β-lactoglobulin

• Particle charge was significantly increased by the presence of calcium.
• The presence of both EGCG and calcium greatly influenced particle size.
• Calcium occasionally affected protein secondary structure.
• Calcium greatly influences the EGCG/β-lg interactions.

Milk proteins such as β-lactoglobulin (β-lg) have been shown to interact with epigallocatechin-3-gallate (EGCG), and possibly offset their degradation. However, currently no studies have taken into account other milk components such as calcium in the EGCG/β-lg interactions. The aim of this study was to characterize the interactions between EGCG and β-lg in a simulated milk ultrafiltrate (SMUF) with and without calcium. Different EGCG concentrations were tested in solutions containing β-lg and made in SMUF in the presence or absence of calcium. Particle size and zeta potential, as well as other measurements were performed on all solutions. Results showed an important increase in particle size and charge when β-lg was in the presence of EGCG. Particle charge grew significantly more negatively in the absence of calcium. It was demonstrated for the first time, to the best of our knowledge, that the presence of calcium greatly impacts the EGCG/β-lg interactions.